Martin O'Neill is facing the prospect of having his Republic of Ireland managerial dream team ripped apart within six months.

The 62-year-old Ulsterman captured the imagination of the nation when he accepted the challenge of replacing Giovanni Trapattoni in November last year and asked Roy Keane to assist him.

However, O'Neill revealed on Thursday evening that the former Republic skipper has held informal talks with Celtic over their vacant manager's job.

Celtic have confirmed they are in discussion with "a number of excellent candidates", with former striker Henrik Larsson and Owen Coyle having preceded Keane as the bookmakers' favourite, but O'Neill, who himself spent five years in charge at Parkhead, is bracing himself for a departure.

He said: "I only reiterate what I said right at the beginning, which I think has been enhanced over this last period of time.

"Roy has been, selfishly, he's been great for me. I've genuinely enjoyed working with him.

"He's sometimes a totally different character to the one that you see on the TV. He's been excellent, the players have enjoyed him immensely.

"I can only say that naturally I'd be disappointed if he left because I really think that he's been terrific.

"We have only had four games with the squad, but he's been excellent and I don't think that he'd give that up lightly."

O'Neill currently has long-term allies Steve Walford and Steve Guppy working alongside himself and Keane, although he insisted their presence - their appointment is temporary as things stand - has nothing to do with the uncertainty over the former Manchester United midfielder's situation.

However, he admitted he always expected his number two to be offered jobs after bringing him in from the football wilderness following an unhappy end to his spell in charge at Ipswich.

O'Neill said: "Even just let's say that it didn't materialise - is that to say that in say October-time, the same situation might not arise?

"You have to be ready for these things. I really thought when I took him on that the period of time that we would have, at some stage or another, he would be offered something.

"I just probably didn't expect things to happen so quickly."

O'Neill indicated at the weekend when the speculation over Keane and Celtic started to gather momentum that he would not stand in his way if the call came.

However, asked if the 42-year-old would leave with his blessing should he be offered and accepted the job, he replied with a smile: "It's a very good point that, depending on how you deal with 'blessing'.

"I would be disappointed, obviously, if he's gone, but a club like Celtic is a very, very big club and maybe sometimes those particular offers might not come around too often."

However, while keen to retain Keane's services, O'Neill did suggest that the prospect of combining roles with Celtic and Ireland might prove a step too far.

He said: "Because it has just arrived really, that sort of thing I haven't really got a chance to speak to him about. I genuinely haven't had a chance to.

"It's a possibility, but if you're a manager of a football club, then I think maybe that sort of thing of coming back and doing something else might be difficult.

"I don't know, is the answer, and I wouldn't dismiss it, but I really have not considered it or given it any proper thought."

News of Keane's talks with Celtic came as a surprise to the Republic players with whom he had just worked at an open training session at the Aviva Stadium on Thursday night.

Speaking minutes after leaving the pitch, striker Kevin Doyle said: "He was part of training and it seemed like he wasn't going anywhere in a hurry.

"I think it's great having him around, personally. Roy, who has been a world-class player, to have him coaching you is nice.

"It brings that extra bit of coverage, it brings a bit more to the Irish team, gives is a buzz for the supporters. Fans love seeing him involved, and it's the same with players.

"But thankfully, we have a manager who is very similar in that regard and he has his assistant who have been with him for a long time, so if Roy takes another job, the set-up is pretty strong to deal with that.

"But it would be nice to keep him here for the (Euro 2016 qualifying) campaign, from a personal point of view."